It is well-known to place a hermetically sealed container with the powder therein in an autoclave or hot isostatic press where it is subjected to heat and gas pressure.
Because of the expense and limitations of an autoclave or hot isostatic press, there have been significant developments made wherein the powder to be compacted is encapsulated in a substantially fully dense and incompressible container providing a pressure-transmitting medium which maintains its configurational integrity while being handled both at ambient temperatures and at the elevated compaction temperatures, yet becomes fluidic and capable of plastic flow when pressure is applied to the entire exterior surface thereof to hydrostatically compact the powder. Typically, the powder is hermetically encapsulated within the pressure-transmitting medium which is thereafter heated to a temperature sufficient for compaction and densification of the powder. After being sufficiently heated, the pressure-transmitting medium with the powder therein may be placed between two dies of a press which are rapidly closed to apply pressure to the entire exterior of the pressure-transmitting medium. The pressure-transmitting medium, at least immediately prior to a selected predetermined densification, must be fully dense and incompressible and capable of flow so that the pressure transmitted to the powder is hydrostatic and, therefore, from all directions, i.e., omnidirectional. After the material is densified to the desired degree, the pressure-transmitting medium defining the container must be removed from the compacted material and in so doing the integrity of the pressure-transmitting medium is lost whereby either the pressure-transmitting medium is no longer usable or must be completely recycled to fabricate a new container.